1. Field
Embodiments relate to semiconductor devices and, more particularly, to a local self-boosting method of a flash memory device.
2. Description of the Related Art
Semiconductor memories are considered to be the most vital microelectronic components of digital logic system design, e.g., in computers and microprocessor-based applications ranging from satellite to customer electronics. Therefore, advances in fabrication of semiconductor memories, including process enhancements and technology developments through scaling for higher densities and faster speeds, help establish performance standards for other digital logic families.
Generally, semiconductor memory devices are categorized as volatile memory devices or non-volatile memory devices. In volatile memory devices, logic information is stored by setting a logic state of a bistable flip-flop in case of a static random access memory (SRAM) or by charging a capacitor in case of a dynamic random access memory (DRAM). In a volatile memory device, data is stored and read while power supply is continued and lost when power supply is interrupted.
Nonvolatile memory devices (e.g., MROM, PROM, EPROM, and EEPROM) can retain their stored data even when their power supplies are interrupted. The data stored state of a non-volatile memory may be permanent or reprogrammable according to applicable manufacturing techniques. A non-volatile memory device may be used for storing programs and microcodes in a wide range of applications, e.g., computers, avionics, communications, and consumer electronic technology industries. If a system requires a non-volatile memory that is reprogrammable and is capable of promptly combining of volatile and non-volatile memory storing modes in a single chip, a non-volatile RAM (nvRAM) may be used for the system. Moreover, a certain memory structure with additional logic circuits has been developed and may optimize performance for an application oriented task.
With non-volatile semiconductor memory devices like MROM, PROM, and EPROM, it may not be easy to erase and write data, and a general user may experience difficulties in updating memory contents. On the contrary, EEPROM may erase and write data electrically without difficulty and may become widely used in system programming for continuous updating and also auxiliary memory devices.
A flash memory device is a kind of EEPROM where a plurality of memory regions called cells can be erased or programmed through a single program operation. A conventional EEPROM enables only one memory region to be erased or programmed at onetime. This means that a flash memory device can operate at a higher and more effective speed. After a specific number of erase operations, all types of flash memories and EEPROM may wear out due to a breakdown of an insulating layer covering charge storage means used to store data.